ECM machine with skewed workpart and pocketed cathodes

ABSTRACT

A machine for electrochemically machining oversize airfoil blades of an integral bladed gas turbine engine rotor includes a yoke assembly on which the rotor is fixtured and which is pivotable to place the lateral center plane of the rotor at an angle or skew relative to the center plane of the machine and opposed cathodes in an electrolyte chamber at a workpart machining position in the chamber. The cathodes have pockets to receive airfoil blades adjacent the individual blade to be machined without contact with the adjacent blades as the cathodes and workpart are moved relative to the workpart machining position during workpart positioning in the chamber and also during advancement of the cathodes from a cathode start machining position toward the workpart during machining. The yoke assembly includes a pivot pin and locking mechanism for releasably locking the angular position of the yoke assembly. The angular relation of the center planes as well as pockets in the cathodes permit full accessing of the individual airfoil blade to be machined by movement of the cathodes in multiple directions.

FIELD OF THE INVENTION

The invention relates to machines and methods for electrochemicallymachining a workpart and, in particular, for electrochemically machininga workpart having a central hub with rotational symmetry and radiallyprojecting appendages, such as airfoils, spaced circumferentially aroundthe hub periphery.

BACKGROUND OF THE INVENTION

Electrochemical machining (ECM) is a well known process for machiningmetallic based workparts and in the past has been employed to machinecomplex airfoil shapes on individual blades and complex airfoil bladesattached to a central cylindrical hub and extending radially therefromaround its periphery.

ECM apparatus for machining individual airfoils projecting from thecentral hub of an integral bladed gas turbine engine rotor or wheel isshown in the Stark et al U.S. Pat. No. 3,523,876 issued Aug. 11, 1970;the Stark et al U.S. Pat. No. 3,714,017 issued Jan. 30, 1973; and theKawafune et al U.S. Pat. No. 3,803,009 issued Apr. 9, 1974. In thesepatents, the airfoils are completely machined by the ECM process out ofa cylindrical blank or disc of material.

The Trager U.S. Pat. No. 3,288,699 issued Nov. 29, 1966 illustrates anECM apparatus for machining in simultaneous fashion multiple airfoilsintegral on a turbine wheel blank or disc wherein during axial advanceof the cathode the workpart (turbine wheel blank) is rotated through aselected angle to impart a curve to the airfoils as they are formed bythe cathode.

The Lucas U.S. Pat. No. 3,970,538 issued July 20, 1976 describes an ECMapparatus for machining oversize leading and trailing edges of airfoilblades integrally cast with a central hub to form an integral bladedrotor for a gas turbine engine. A special cathode structure is disclosedto ECM the leading and trailing edges.

Other prior art works have employed ECM apparatus to machine a pluralityof airfoil blades from one piece of elongated stock material orindividual airfoils one at a time. For Example, the Wilson et al U.S.Pat. No. 4,256,555 issued Mar. 17, 1981 illustrates ECM'ing anindividual airfoil shaped blade perform using opposed cathodes which arecaused to move toward opposite sides of the blade preform by movablearms or rams on a conventional machine. In the past, a ball screwassembly driving by a servomotor has been employed to drive each ramwith the cathode thereon. In the patent, the cathode rams are driven inopposed directions at a 45° angle relative to the centerline of theblade. The Goodwin U.S. Pat. No. 3,309,294 issued Mar. 14, 1967illustrates an ECM apparatus for shaping an individual metallic airfoilblade for an axial flow compressor of a gas turbine engine.

The Schrader U.S. Pat. No. 4,052,284 issued Oct. 4, 1977 illustrates anECM apparatus for at least partially forming a plurality of airfoils ina workpart. The apparatus includes a plurality of separately movableelectrodes, each pair of electrodes being movable along paths definingan acute angle relative to the sides of the workpart. The Schrader U.S.Pat. No. 4,057,475 issued Nov. 8, 1977 describes a ECM method forforming a plurality of airfoils in a single workpiece. The Schrader etal U.S. Pat. No. 4,167,462 issued Sept. 11, 1979 describes a controlsystem for an ECM machine having a plurality of electrodes driven by aplurality of identical hydraulic pumps.

The Sanders U.S. Pat. No. 3,060,114 issued Oct. 23, 1982 discloses anECM machine and method using a reciprocating cathode structure. TheInoue U.S. No. 4,405,721 issued Mar. 12, 1985, illustrates a multipleaxes electrical discharge machine for forming a three dimensional cavityin a workpart.

SUMMARY OF THE INVENTION

The invention contemplates an apparatus for electrochemically machininga workpart of the type having appendages extending from and spacedtherearound wherein means is provided for positioning an individualappendage at a workpart machining position in the electrolyte chamberwith the workpart and cathode means disposed in the electrolyte chamberand skewed at an angle relative to one another at the workpart machiningposition and wherein the cathode means includes pocket means thereon toreceive an appendage adjacent to the individual appendage as theindividual appendage is positioned at the workpart machining positionwithout contact so as to allow full cathode access to the individualappendage for machining. The adjacent appendages remain received withoutcontact in the pocket means during machining of the workpart. Means isprovided for moving the cathode means relative to the workpart machiningposition as the workpart is positioned.

In a typical working embodiment of the invention, a slide meanspivotally carries the workpart at the selected skew or angle to thecathode center plane relative to the workpart machining position andpositions workpart appendages in the electrolyte chamber at said angle.The slide includes a pivot pin and clamp which can be releasably lockedat the selected center plane angle. Opposed pocketed cathodes in theelectrolyte chamber are movable in respective directions toward oneanother and toward respective sides of a selected individual workpartappendage and in other directions transverse thereto as the workpartappendage is positioned in the chamber. Pockets in the cathodes receivethe workpart appendages adajcent to the individual appendage to bemachined without contact. The adjacent appendages remain in the cathodepockets out of contact with the cathodes during the machining process asthe cathodes move from a cathode start machining position to a cathodefinish position. The combination of the workpart center plane angle orskew and movement of the cathodes in multiple directions with eachcathode having a recessed pocket to receive the adjacent appendageswithout contact permits full accessing of the cathodes to the respectivesides of the individual workpart appendage for machining the entirelateral surface thereof. Preferably, electrical insulating means isprovided in the recessed pockets for preventing electrical current flowbetween the adjacent appendages and the adjacent cathode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective, schematic view of an integrally bladed rotor(IBR) for a gas turbine engine.

FIG. 2 is a plan view of a portion of FIG. 1.

FIG. 3 is a schematic perspective view showing the spatial relationshipof the IBR and its center planes to the cathode center plane and machinecenter plane and the difficulty of access to the airfoil blade A to bemachined.

FIG. 4 is a front elevation of the machine of the invention forelectrochemically machining an IBR with integral preformed oversizedairfoil blades to finish dimension.

FIG. 5 is a side elevation of the machine of FIG. 4 in the direction ofarrow 5.

FIG. 6 is a plan view of the machine of FIG. 4 in the direction of arrow6.

FIG. 7 is an enlarged side elevation of a portion of the machine in thedirection of arrow 7.

FIG. 8 is an enlarged front elevation of a portion of FIG. 4.

FIG. 9 is a side elevation of a portion of FIG. 8 with a portion insection.

FIG. 10 is an enlarged view of FIG. 7 with components removed and otherstaken in section to show the X-axis slide drive.

FIG. 11 is an enlarged elevation of another portion of FIG. 3 with aportion in section.

FIG. 12 is an elevation of a portion of FIG. 11 taken in the directionof arrows 12.

FIG. 13 is a sectional view taken along line 13 of FIG. 11.

FIG. 14 is an enlarged side elevation of a portion of FIG. 11 in thedirection of arrows 14 with the cathode support structure and certainclamp features removed.

FIG. 15 is an elevation of FIG. 14 taken in the direction of arrows 15with a portion in section.

FIG. 16 is an enlarged view of portion 16 of FIG. 14.

FIG. 17 is an enlarged elevation of a portion of FIG. 4 with portions ofthe electrolyte chamber and vertical slide yoke broken away.

FIG. 18 is an elevation taken in the direction of arrows 18 in FIG. 17.

FIG. 19 is a sectional view taken along line 19 of FIG. 18.

FIG. 20 is a side elevation of FIG. 18.

FIG. 21 is a sectional view of FIG. 18 along line 21.

FIG. 22 is a sectional view taken along 22 of FIG. 17.

FIG. 23 is a sectional view taken along arrows 23 of FIG. 22.

FIG. 24 is a front elevation of the sealing shroud.

FIG. 25 is a bottom elevation of the sealing shroud.

FIG. 26 is a sectional view taken along line 26 of FIG. 24.

FIG. 27 is a sectional view taken along line 27 of FIG. 26.

FIG. 28 is a sectional view similar to FIG. 26 of another embodiment ofthe arbor.

FIG. 29 is a front elevation of the concave cathode assembly.

FIG. 30 is a front elevation of the convex cathode assembly.

FIG. 31 is a plan view of FIG. 29 of the concave cathode.

FIG. 32 is a plan view of FIG. 30 of the convex cathode.

FIG. 33 is a side elevation of the tip seal block.

FIG. 34 is a plan view of FIG. 33.

FIG. 35 is an end view of FIG. 34.

FIG. 36 is a projection of FIG. 35.

FIG. 37 is a partial sectional view of structure 34 taken along lines 37of FIG. 22.

FIG. 38 is a plan view of the electrical continuity clamp mechanism forengaging the indexer shaft 652.

FIG. 39 is an elevation of FIG. 38.

FIG. 40 is an end view partially broken away of FIG. 38.

FIG. 41 is an elevation of the clamp itself.

FIG. 42 is a perspective view of the cathodes and IBR illustratingtypical movements of reference centerlines R1 and R2 of the cathodes aswell as movement of the IBR involved in the ECM method with thebi-directional movement of centerline R2 broken down into right X and Yaxes components in the side projection thereof.

FIG. 43 is a partial sectional view of the IBR.

FIG. 44 is an elevational view looking from the tip of the blade 16' toroot with cathode positions superimposed to show relative spatialrelationships therebetween at a coordinated position.

FIG. 45 is a view similar to FIG. 44 but with the cathodes and IBR at acathode machining position.

FIG. 46 is a view similar to FIGS. 44 and 45 but with the cathodes at afinish position.

FIG. 47 is a tip to root elevational view showing a finished blade.

DESCRIPTION OF BEST MODE OF CARRYING OUT THE INVENTION

Shown in FIGS. 1 and 2 is an integrally bladed rotor 10 (hereafter IBR)for a gas turbine engine. The IBR 10 includes a central cylindrical hub12 with a through-hole 14 for receiving a shaft (not shown) by which theIBR is mounted in the compressor section of a gas turbine engine as iswell known for rotation about its longitudinal axis R. Projectingradially from and spaced apart circumferentially around the hub is aplurality of twisted airfoil-shaped blades 16. Each blade 16 includes afirst convex lateral side 18, a second oppositely facing concave lateralside 20 and leading and trailing edges 22,24, respectively. Platformareas 23 extend from fillet radii 25 where each blade joins the hub 12.

The IBR shown may be formed in various known ways; e.g. it may be amachined structure, unitary cast structure, a composite structure wherethe blades 16 are preformed and the hub cast therearound to form anintegral structure, a composite structure where the blades 16 areattached metallurgically to the hub, or a superplastically forgedstructure where the blades 16 are formed integrally with the hub from acommon forging blank. Regardless of the technique employed to fabricatethe IBR, the blades 16 will be preformed to an oversize shape orenvelope E (FIGS. 44-45) requiring further machining to precisedimensional tolerances for use in a gas turbine engine.

The machine of the invention will be described hereinbelow with respectto the finish or semi-finish machining by the ECM process of theindividual oversize blades or preforms 16 of the IBR. The machine to bedescribed finish machines the blades one at a time with the entirelateral sides 18,20 as well as leading and trailing edges 22,24, filletradii 25 and platform areas 23 adjacent radii 25 being machined.

FIG. 3 illustrates somewhat schematically the spatial relationshipsinvolved between the IBR and machine features. For example, it can beseen that the IBR 10 is positioned with its lateral center plane W(plane through its thickness perpendicular to the center plane of thegas turbine engine in which it will operate and containing bladecenterline F) at an angle B relative to the machine center plane P shownalso in FIG. 3 as a vertical plane through the center of the machine. Aswill be explained below, the IBR 10 is fixtured to pivot about verticalaxis V in its lateral center plane W so that the IBR center plane Brelative to the machine center plane P can be varied within a selectedrange; e.g. 0°-45°, to plane the centerline or stacking line F ofairfoil blade 16' to be machined substantially within machine centerplane P when the blade is at a workpart machining position M.

FIG. 3 also reveals that the cathode center plane CC is orthogonal tothe machine center plane P when the blade is at the workpart machiningposition M and the cathodes are at the cathode or start machiningposition (also see FIG. 45) spaced on opposite sides of the blade. Thecathode center place CC is the plane therethrough that is orthogonal tothe machine center plane P and that passes through the verticalcenterline F of the airfoil blade at the workpart machining position M.The cathode feed axes or directions, right X-axis and left X-axis, arelocated at an inclined angle relative to horizontal; e.g. the X axes areoppositely inclined at a 30° angle relative to horizontal as shown.

Referring to FIGS. 4-6 and 22, a machine constructed in accordance withthe invention is shown having a base 30 on which a generally C-shapedsupport 32 is fixedly mounted. Mounted on the top surface of base 30 isa structure 34 enclosing and forming therewithin an electrolyte chamber36. The structure 34 includes a first rectangular front plate 38 withrectangular opening 40, a back plate 42 and first and second lateralside plates 44,46. A front cover plate 48 is releasably fastened to thefront plate 38 by machine screws 50 to cover and close off opening 40and carriers electrolyte back-pressure member 49 with slots 49acommunicating with chamber 36 and a drain opening 60 for electrolyteremoval after it passes between the blade to be machined and cathodes. Abottom plate 52, FIG. 11, closes off the bottom of the electrolytechamber 36 and a top plate 54, FIG. 18, to be described in detailhereinafter closes off the top thereof except for an opening 56 toreceive a portion of the IBR as will be explained.

Bottom plate 52 includes a drain opening 60 to receive electrolyte afterit passes over the airfoil blade being machined for recirculation to thefiltering equipment (not shown) for reuse in the ECM process.

As is apparent from FIG. 22, the electrolyte chamber forming structure34 includes a front side 70 which is substantially parallel with backside 72 and first lateral side 74 which is substantially parallel withsecond lateral side 76.

A front basin 80 with its own drain fitting 82 is provided on the frontof base 30 to catch electrolyte when front cover plate 48 is removed andto drain the electrolyte back to the filtering equipment.

As shown best in FIGS. 4-7 and 11, identical parallel first (left) andsecond (right) Y-axis slideways 90,92 and mating first (left) and second(right) Y-axis slides 94,96 are disposed adjacent first and secondlateral sides 74,76, respectively, in substantially parallel relationthereto. The Y-axis slideways and associated slides are also parallel tomachine center plane P. Positioned between the slideways 90,92 and theirrespective slides 94,96 are two rows of roller bearings 100 with theaxes of the bearings inclined in opposite directions as shown toeliminate lateral play and movably mounted each slide 90,92 on itsrespective slideway 90,92. The roller bearings 100 are mounted between afixed longitudinal race 91 and longitudinal race 93 movable with slide94 or 96 as the case may be.

Movement of slides 94,96 along the respective slideways 90,92 is in theso-called right Y-axis or direction or left Y-axis or direction.Identical ball screw mechanisms are employed to drive the slides 94,96on the Y-axes or directions as will be explained.

Each Y-axis slide 94,96 carries a cathode support structure 100 andcathode mechanism 102 which are identical to the other although orientedin the opposite right and left axis directions on the respective slides94,96 as shown in FIG. 4. As a result only the cathode support structure100 and cathode mechanism 102 on the right slide 96 will be described,it being understood that the same cathode support structure and cathodemechanism is mounted on and movable with slide 94.

Referring to FIGS. 11-13, the cathode support structure 100 is shownincluding a horizontal frame plate 110 affixed directly on slide 96, avertical frame plate 112 affixed to horizontal frame plate 110 and anoutwardly inclined frame plate 114 also affixed to horizontal frameplate 110.

A ball screw/nut housing 120 is mounted on cross frame members122,123,125 attached between the vertical frame member and outwardlyinclined frame member. Inside the housing 120 is a conventional ball nut124 inside of which is received a ball screw 126 with recirculatingballs (not shown) therebetween in known manner. Busses 121 extend from aconventional source of electrical power and are fastened to housings 120to provide the proper polarity electrical potential between the cathodemechanisms 102 and IBR 10 which is made the anode for ECM'ing.

The ball screw 126 has an end 126a mounted in ball bearing assemblies128 in the outwardly inclined frame member 114. End 126a is keyed by key132 to a drive shaft 134 on which worm wheel 136 is mounted. Drive shaft134 is rotatably mounted by bearing assemblies 135 in a housing 137affixed to inclined frame member 114. Worm wheel 136 is driven inrotation by worm gear 138 on the output shaft 140 of D-C servomotor 142.Rotation of ball screw 126 of course causes ball nut 124 to translate inhousing 120.

In particular, ball nut 124 is fastened by machine screws 148 (only oneshown) to hollow cathode ram 150 which is supported for sliding movementin hollow bushings 152 and 154, which are coaxially aligned fortranslation of the ball nut along the right or left X-axis direction bythe ball screw. As shown, the right cathode ram 150 and bushings 152,154extend at an angle of inclination relative to vertical; e.g. 30°. Ofcourse, the left cathode ram and associated bushings are inclined at anangle of inclination of 30° relative to vertical but in the oppositedirection or sense. Of course, the right and left X-axes are orthogonalto machine center plane P when viewed in plan.

An indicator plate 160 is attached to cathode ram 150 for movementtherewith and indicator plate 160 carries another indicator supportplate 162 with it for purposes to be explained below.

As shown, hollow bushing 154 is mounted in a bushing support member 166affixed by machine screws 168 to the vertical frame member 112, FIG. 14.The hollow bushing 154 terminates at its upper open end at an open-endedcollar 170 received in a rectangular, flat-sided bore 172 in lateralside 76. Collar 170 has a complementary rectangular outer shape to fitin bore 172 and includes an annular flange 170a fastened by machinescrews 176 to side plate 46. For reasons to be explained below, theinner diameter of the cylindrical inner bore of collar 170 is largerthan the outer diameter of cylindrical cathode ram 150 which is thusreceived with clearance therein for movement along the right X-axisdirection and importantly also in the right Y-axis direction orthogonalthereto. Of course, vertical frame member 112 also includes a bore 112ato receive the hollow bushing 154.

The cylindrical ram 150 terminates at an end 150a which has fastenedthereto via a machine screw (not shown) and threaded hole 150b a cathodesupport block 180 which is received with clearance for sliding movementin the right X-axis and Y-axis directions in the rectangular, flat sidedbore or channel 172 in lateral side plate 46 as described in detailhereinafter. The cathode support block 180 has sides complementary inshape to those of channel 182 for such sliding movement.

As is apparent in FIG. 11, multiple o-ring seals 190 are employed toprevent entry of dirt and foreign matter into the hollow busings 152 and154. And, as shown best in FIGS. 11, 14 and 22, a rectangular seal 192is positioned between lateral side 74 and the vertical frame member 112.The purpose of this seal 192 well be explained below.

From the detailed description thus far, it is apparent that the rightand left vertical frame members 112 are movable in the respective rightand left Y-axis or direction relative to and substantially parallel tothe lateral side 74 or 76 of the electrolyte chamber-forming structure34.

As shown best in FIGS. 12-13, indicator support plate 162 movable withindicator plate 160 carries set screw 191 for controlling movement ofthe cathode ram 150 toward electrolyte chamber and set screw 193 forcontrolling movement of the ram away from the chamber. Set screws191,193 engage limit switches 195,197, respectively, which switchescontrol over-travel of respective ram drive motors 142. Of course, setscrews 191,193 are adjustable by threading them relative to limitswitches 195,197. Limit switches 195,197 are mounted on vertical crossframe member 127 which is attached to vertical cross frame member 125. Adial micrometer 199 is also carried on indicator support plate 162 toengage with stop 201 on bushing support member 166 to display the amountof travel of the cathode ram in the respective right and left X-axisdirection.

During the ECM process there is a need to releasably retain or lock theposition of the right and left vertical frame members 112 and thus ofcourse slides 94,96 and cathode rams 150 in the right and left Y-axes ordirections. To this end, releasable retaining means is provided in theform of four cylindrical studs 200 arranged in a square pattern on thelateral sides 74,76 of the electrolyte chamber-forming structure 34, inparticular, at the corners of a square array as shown in FIGS. 4,5, and14 for the right side 76. Each stud 200 is attached in fixed position tolateral side 76 by a lock collar 202 and associated machine screws 204.The studs are of a length sufficient to extend past the free surface112a of the vertical frame member 112, as shown in FIGS. 14-16. Inparticular, each stud 200 extends through oval slots 210 in frame member112 and through a cylindrical bore 212 of a washer 214 and through ovalopening 215 in oval wear plate 216 positioned beneath the washer 214.Washer 214 includes a small radius curvilinear central shoulder 218 forpurposes to be described. Of course, the washer 214 and wear plate 216move with the vertical frame member 212 in the Y-axis or directionrelative to the associated studs 200 extending therethrough. Oval wearplate 216 is fastened to frame member 212 by machine screws 217.

Adjacent the free end of each stud 200 is a cross-pin 220 by which aclevis 222 is pivotally connected to each stud 200. As shown best inFIG. 15, the cross-pin 220 is eccentrically located relative to largeradii cams 224 on the clevis. The cams 224 engage and contact thesmaller radius central shoulder 218 of each associated washer 214. Eachclevis 222 itself is pivotally connected by cross-pin 228 to the outputshaft 229 of a pneumatic or other fluid cylinder 230. Each cylinder isin turn pivotally mounted by cross-pin 232 to a bracket 234 affixed toelectrolyte chamber-forming structure 34. In particular, the upper andlower cylinders 230 nearest the front of the machine are pivotallyconnected to brackets 234 affixed to front plate 38 by machine screws236.

As seen best in FIGS. 4, 5 and 7, the upper and lower cylinders 230nearest the back of the machine are pivotally connected to brackets 234affixed to back or rear plate 42 of the structure 34 by machine screws242.

When all the upper and lower cylinders 230 are actuated to retract theiroutput shafts 229, each clevis 222 will be pivoted or rotated in FIGS.13-15 to the clamp position shown in solid from the release positionshown in phantom to cause the large radius cams 224 to eccentrically camagainst smaller radius central shoulder 218 to force the vertical framemember 112 toward and against lateral sides 74,76 of structure 34 toreleasably retain a selected position of the cathode support structure100 along the right and left Y-axes or directions. Of course, retentionor clamping of frame member 112 also clamps the associated slide 94,96and cathode ram 150 in a selected right or left Y-axis position. Whenthe right and left frame members 112 are thusly clamped, the rectangularseals 192 between lateral side 74,76 and the associated facing framemember 112 are compressed to effect positive sealing therebetween toprevent any potential electrolyte leakage therepast. Each seal 192,however, performs its sealing function even when the associated right orleft vertical frame member 112 is moving along its Y-axis.

The mechanisms for moving right and left Y-axis slides 94,96 areidentical and that for moving slide 96 is shown in FIG. 10 as includingan DC servomotor 260 with output shaft 262 keyed by key 264 to hollowshaft 266 of a conventional gear reducer 268. The gear reducer 268 inturn drives a conventional ball screw 270 mounted in housing 272 in thesame manner as ball screw 126 is shown mounted in inclined frame member114 in FIG. 11. The ball screw 270 cooperates with and drives intranslation a ball nut 274 fastened by machine screws 276 to a verticalplate 278 attached on horizontal frame member 110. Thus, slide 96 and 94are driven along the respective right and left Y-axis or direction bythe respective DC servo drive motor and ball screw arrangementdescribed.

As mentioned hereinabove, cylindrical hollow cathode ram 150 terminatesat and is fastened to a cathode holder or support block 180 which isreceived for sliding bi-directional movement in the rectangular,flat-sided channel 172 in lateral side plate 46. Each cathode supportblock 180 has a cathode assembly 300 attached thereto as shown best inFIG. 17 so that each cathode mechanism or means 102 includeselectrically conductive cathode assembly 300, cathode block 180, andcathode ram 150 receiving current through housings 120. Each assembly300 (FIGS. 29 and 30) comprises a cathode holder 302 and either theconcave cathode 304 or convex cathode 306 attached thereto as shown bestin FIGS. 31 and 32. The cathode holders 302 for each cathode areidentical in construction except that features are spatially in reverse.Each holder 302 includes a support plate 310 and filler plate 312attached together by machine screws (not shown) in threaded bores 314(only one shown). Each support plate includes a keyway or slot 316facing the cathode support block 180 when assembled therewith andmultiple threaded holes 318 to receive machine screws (not shown) bywhich the cathode holder is attached to the cathode support block 180.Threaded holes 180a, FIG. 11, in the cathode support block 180 receivethese machine screws. The convex and concave cathodes 304 and 306 aresimilarly attached to the cathode support plate 310 by multiple dowels322 received in holes 324,326 in the support plate and cathode and alsoby multiple machine screws 327 (only one shown) received in tapped holes329,331 (only one of each shown) in the support plate and cathode inline with the dowel holes, FIG. 30.

Convex cathode 306 includes an inner concave working face 330 configuredcomplementary to the convex lateral side 18 of the airfoil blade 16 tobe machined and dimensioned so as to ECM the desired precise toleranceson that side 18 in the ECM process. Convex cathode 306 includes flat,substantially parallel sides 332,334 extending from the working face toand conextensive with the flat sides 310a,310b of the cathode holder302. In the top surface 336 of the convex cathode is a recess or pocket340 shaped and having a depth to receive an airfoil blade immediatelyadjacent the one 16' to be machined by the convex cathode as will beexplained. The top surface 336 and bottom surface 342 of the convexcathode are flat and substantially parallel as shown best in FIGS. 30and 32.

Concave cathode 304 includes an inner convex working face 350 configuredcomplementary to the concave lateral side 20 of the airfoil blade 16 tobe machined and dimensioned so as to ECM the desired precise toleranceson that side 18 in the ECM process. Concave cathode includes flat,substantially parallel sides 354,356 and flat, substantially paralleltop and bottoms sides 358,360, FIGS. 29 and 31, with a recess or pocket362 in the top side shaped and having a depth to receive an airfoilblade immediately adjacent the one being machined by the concave cathodeas will be explained.

Cathode pockets 340,362 have an electrical insulating layer or coating340a,362a over the entire pocket surface to prevent unwanted strayelectrical current flow to blades 16 adjacent 16' during machiningthereof as will be explained.

The electrolyte chamber 36 with the cathode assemblies 300 therein isshown best in FIGS. 17 and 22. It can be seen that the bottom flat sidesof the cathode support blocks 180 and cathode holder 302 slide overoppositely inclined flat surfaces 400 of guide block 402. Mountedcentrally on guide block 402 is a tip seal block 404 made of G10glass/epoxy material. The tip seal block 404 is located on the guideblock 402 by two coaxial keys 408, FIGS. 16 and 31, and extends upwardlytoward the cathodes 304,306 in the electrolyte chamber 36.

As shown best in FIGS. 33-36, the tip seal block 404 includes oppositelyinclined flat guide surfaces 410,412 on which the flat bottom sides342,358 of the cathodes are sealingly guided during cathode movement.The inclined guide surfaces 410,412 are inclined at the same angle, 30°,that the inclined flat surfaces 400 of guide block 402 are inclined. Inthe central portion of the tip seal block 404 is a tip seal member 420configured and oriented to locate and sealingly contact the tip of theairfoil blade 16' which is to be machined between the cathodes 304,306.The tip seal member 420 is oriented at the desired angle of the bladetip to effect this locating and sealing contact action. The tip sealblock 404 is mounted to the guide block 402 by multiple machine screws403 in tapped holes 422 so that different tip seal blocks 404 can beused for IBR's with different airfoil blade designs.

As shown best in FIG. 17, the top surfaces of the cathode support block180 and cathode holder 302 are guided during cathode movement byoppositely inclined guide surfaces 428,429 on a electrolyte chambercover 54 which is shown in FIGS. 18-21 and is described hereinbelow.

As shown best in FIGS. 22 and 23, transverse oppositely inclinedchannels 431,433 are formed in the structure 34 by channels 172 in sideplates 44,46, by the guide block 404, by the guide surfaces 428,429 ofthe cover 430 and by the inner wall 450 of front plate 38 and inner wall452 of back or rear plate 42. As is apparent, the cathode ram 150,cathode support block 180, cathode holder 302 and the respective cathode304,306 attached thereto move in the opposing inclined channels 431,433.Of course, channels 431,433 incline toward one another at a 30° anglerelative to horizontal.

Electrolyte flow is introduced between the cathodes 304,306 throughelectrolyte inlet opening 440 in the rear plate 42. As shown in FIGS. 17and 22, the inlet opening 440 extends transverse to the direction ofcathode movement in channels 431,433 and toward the working faces330,350 of the cathodes 304,306. The electrolyte from inlet opening 440flows between the cathode working faces 330,350 and lateral sides 18,20of the airfoil blade being machined and into depending drain hole 60 infront plate 38 during movement of the cathodes from the start machiningposition to the finish position. Intimate contact between guide block408 and guide surfaces 428,429 and the cathode support block, cathodeholder and cathodes prevent electrolyte leakage therepast during the ECMprocess when the cathodes move from the start machining position to thefinish positions as will be explained. Similarly, contact between innerwall 450 and the cathode support block and cathode holder preventelectrolyte leakage therepast.

However, between the inner wall 452 of the rear plate 42 and rearsurfaces of the cathode support block cathode holder and cathodes is aclearance space 460 which is substantial (e.g. 1 inch) to provide forthe Y-axes cathode movement. In order to seal off this space 460 andalso to direct and form an electrolyte flow path toward the airfoilblade, first and second sealing pistons 470,472 are movably mounted onthe rear plate 42 for movement transverse (orthogonal) to channels431,433 to sealingly engage the flat rear sides of the cathode supportblock, cathode holder and cathodes to prevent electrolyte leakagetherepast during machining. The sealing pistons are identical exceptthat certain features are spatially reversed as shown. As best seen inFIG. 11, a bottom inclined side 471 of each sealing piston sides onblock 402 whereas a top inclined side 473 rides on guides surfaces 228during such transverse movement. The front surfaces 475 of the sealingpistons are flat, planar to sealingly contact the rear flat surface ofeach cathode 304,306. The sealing pistons 470,472 carrying a pair ofo-ring seals 474 and are actuated to slide in the transverse directionby first and second hydraulic or fluid cylinders 480 mounted on theoutside of the rear plate 42. The piston rods 484 of the cylinder areconnected to shafts 428 attached to the sealing pistons.

As stated above and hereafter, the cathodes 304,306 and cathode holdersare positioned in the fully forward right and left Y-axis positions asshown in FIG. 22 against inner wall 450 of front plate 38 at theinception of ECM machining (at the cathode start machining position,FIG. 45) by advancing the cathodes along their respective slides 94,96.It can be seen that the sealing pistons close off the channels 431,433between the inner wall 452 of back plate 42 and the rear sides of thecathodes and cathode holders. The sealing pistons are moved into suchsealing engagement shown when the cathodes are placed in the machiningposition from the coordinated position as described below prior toadvancement of the cathodes toward one another and the blade 16' alongthe respective right and left X-axes and turn on of electrolyte flowfrom inlet 440.

Electrolyte is supplied to inlet opening 440 under high pressure by aconventional pump (not shown) and electrolyte tank (not shown).

Referring to FIGS. 18-21, the cover 54 for the electrolytechamber-forming structure 34 is shown including a top plate 500 andinserts 502,504 and 506 fastened thereto by machine screws as shown witha sealing member 510 extending therebetween as shown. Top plate 500 andinserts 502,504,506 are made of G10 glass/epoxy material.

It is apparent that aforementioned guide surface 428,299 are provided oninserts 502,504, respectively. It is also apparent that top plate 500includes a generally rectangular recess 520 when view in plan and thatsmaller recesses 522 and 524 constituting opening 56 are disposed in thebottom of recess 520 through top plate 500 and inserts 502,504,506.Recesses 522 and 524 are generally rectangular in plan and generallysemi-circular in elevation as shown. Disposed in the bottom of recess520 outwardly of and around recesses 522,524 is a seal 530 for purposesto be explained.

The cover 54 is fastened to the top of the structure 34 by multiplemachine screws 532. When so fastened, recess 524 is adapted to receive aportion of the hub 12 of the IBR 10 whereas recess 522 is adapted toreceive the several airfoil blades 16 projecting radially from the hub.As is apparent, recess 522 opens at the bottom to the electrolytechamber 36 so that those blades project into the chamber. Recess 522 isintricately configured as shown to accommodate the twisted airfoilblades of the IBR and its configuration may vary depending upon the IBRand IBR blades being machined. Inserts 502,504,506 are replaceable withothers of different shape to accommodate other IBR's. From FIGS. 18 and37, it is apparent that inserts 504,506 are shaped to provide anelectrolyte flow channel 540 which narrows as it approaches blade 16' tobe machined. Likewise, inserts 502,504,506 form an electrolyte dischargechannel 542 which widens to convey electrolyte to drain 60.

A chamber 550 is thus provided by the top plate 500 and inserts502,504,506 into which the cathodes 304,306 can be moved on oppositesides 18,20 of the blade 16 being machined. The end stroke finishposition (see FIG. 46) of the cathodes 304,306 in this chamber isillustrated in FIG. 17.

As shown in FIGS. 5, 6 and 9, the C-shaped frame 32 includes a pair ofparallel vertical slideways 600 on which a pair of parallel verticalslides 602 are slidably mounted. Vertical slides 602 are affixed to asupport structure 604 comprising vertical rear support member 606, upperhorizontal support member 608 and lower horizontal support member 610. Apair vertical stiffener member 612 extend toward the front of themachine between horizontal members 608,610. As a result of being mountedto slides 602, the support structure 604 is movable in the veritcal orZ-axis or direction. The Z-axis slides and support structure are movedvertically by means of a ball screw 611 driven by a DC servomotor 613.In particular, a worm gear 614 on the motor output shaft 616 drives aworm wheel 618 on a drive shaft 620 keyed to the upper end of the ballscrew 611. A ball nut 622 is affixed on horizontal support member 608 tocomplete the drive mechanism for the Z-axis slide.

The support structure 604 pivotally carries a yoke assembly 630 on whichthe IBR is carried. In particular, yoke assembly 630 includes ahorizontal yoke member 632, a rear vertical yoke member 634 and a frontvertical yoke member 636. As shown best in FIG. 9, the horizontal yokemember 632 is pivotally supported relative to lower horizontal supportmember 610 by a flanged cylindrical pivot pin 638 extending therethroughas shown. Pivot pin 638 is clamped against angular movement by clampcollar 640 and machine screws 642 engaging ring member 644 around theupper end of the pivot pin. The yoke assembly 630 can be angularlyadjusted for reasons to be explained by loosening machine screws 642,rotating the yoke assembly 300, pivot pin 638 and collar 640 the desireddegrees and then tightening the machine screws 642 to releasably lockthe adjusted position of the yoke assembly.

Positioned between the horizontal yoke member 632 and lower supportmember 610 and fastened to the latter is an insulator plate 646 ofelectrical insulating material such as well known G-10 glass/epoxycomposite material to prevent electrical current flow to the supportstructure 604.

The centerline or pivot axis of the pivot pin 638 is coaxial with theline of intersection of the machine center plane P and cathode centerplane CC as well as centerline of blade 16' being machined.

The yoke assembly 630 carries and supports an electrically conductiverotary arbor 650 and indexer stub shaft 652 between the front and rearvertical yoke members 634,636 as shown best in FIGS. 26 and 28. Inparticular, the front end 650a of the arbor shaft is received in anelectrical insulating bushing 656 in the vertical yoke member 636. Therear end of the arbor is received and releasably retained by key 659 inthe copper socket member 660 attached to copper indexer shaft 652 forincremental rotary indexing of the arbor by the indexer shaft. Indexershaft 652 is in turn attached and keyed by key 671 to a drive shaft 673.The output shaft 653a of a conventional gear reducer is attached andkeyed by key 675 to the drive shaft 673 which is made of electricalinsulating material to electrically isolate the gear reducer 653 andindexing motor 670 from the indexer shaft.

The socket member 660 includes a plurality of radial slots 662 intowhich a locking plunger 664 of a cylinder 666 is received to releasablylock the angular position of the arbor. In lieu of slots 662 andplungers 664, the angular position of the arbor can be set by indexingthe arbor with a numerically controlled servomotor.

The indexer shaft 652 is driven in angular increments by the outputshaft of the gear reducer 653 which is driven by D. C. motor 670, FIGS.5 and 38-40. Electrical bus bar 676 carriers D.C. electrical current forthe ECM process from a supply to a frame 678 on which the gear reduceris mounted, FIGS. 38-40. The buss 676 is mounted to copper support frame678 by brass buss retainer 677 having hub 677a. The D.C. electricalcurrent of proper polarity to make the IBR an anode passes through theframe 678 and through indexer shaft 652 to the arbor 650 on which theIBR is supported. Indexer shaft 652 is electrically insulated from theyoke assembly 630 by bushing 686. To insure good electrical contactbetween the indexer shaft and buss bar 676, a copper clamp 681 (FIG. 41)is mounted by machine screws 679 on copper support frame 678 and copperside rails 678a. The clamp 681 has slot 681a between upper and lowerarms 681b,c and can flex about aperture 681d. A threaded nut 683 iscarried in another slot 681g of the clamp. The double-acting cylinder680 includes threaded housing 680a mounted on upper arm 681b of theclamp. The cylinder 680 has a plunger 682 with threaded end 682athreadably engaged in nut 683. Actuation of air cylinder 680 in onedirection causes its plunger 682 to rise and tightly flexibly closeclamp 681 around the rear end of copper indexer shaft 652. The clamp isreleased by reverse action of the plunger in the other direction andalso the resilient spreading action of the clamp about aperture 681d.This shaft clamping action also serves as locking function with respectto locking the rotary indexed position of the shaft 652 and arbor duringthe ECM process. Insulator blocks 685 are positioned between conductivemounting plates 687 and vertical yoke member 634 to electricallyinsulate D.C. motor 670.

It is apparent that clamp 681 includes the upper and lower arms 681b,cwhich define bore 681f therebetween in which the rear end of indexershaft 652 is received for clamping.

The indexer shaft 652 is rotatably mounted in busing 686 in the rearvertical yoke member 634.

As shown best in FIG. 26, the arbor 650 carries on it a locator sleeve690, a clamp sleeve or ring 692, locking nut 694 and spacer 696. Assealing shroud 700 includes a rear portion 702 carried directly on thearbor and a front portion 704 carried on the clamp sleeve 692. Fastenedto the radial shoulder 690a of the locator sleeve 690 is an annular lockring 706 having locating keys 708 (only one shown). A plurality ofcircumferential machine screws 701 and dowel pins 703 extend betweenlocator sleeve 692 and lock ring 706 for proper alignment therebetween.

As is apparent, the hub 12 of the IBR 10 rests on the cylindricallocator hub 706b of the locator sleeve 706 with keys 708 locating onradially disposed and circumferentially disposed slot 10a of the IBR.The radial annular flange 692a of the clamp sleeve is brought up tightagainst the IBR hub 12 by rotation of locking nut 694 to further lockthe position of the IBR on the arbor. Since the arbor, locator sleeve,clamp sleeve are all electrically conductive, the IBR receives the ECMD.C. current through these members during the ECM processes.

As also shown in FIG. 26, the sealing shroud 700 made in part of the G10material encloses the IBR except for the portion 10a of the IBRextending through the rectangular bottom opening 710 of the shroudflange portion 720. The shroud rear portion 702 and front portion 704are releasably fastened together by a plurality of threaded captivescrews 722 spaced circumferentially therearound, FIG. 24. Two guide pins724 in bushing 723 in front portion are disposed between the shroud readand front portions to proper alignment thereof. The rear portion andfront portion of the shroud include generally circular seals 730,732 tosealingly engage annular rims 10b, 10c on the IBR. A seal 734 ofcircular arc shape is provided between the front and rear portions ofthe shroud as shown.

The front face of the front portion of the shroud 700 has an opening 721through which the arbor and clamp sleeve pass and also carries a pair ofhandles 740 by which the front portion can be removed after the bolts722 are removed to allow the IBR to be removed from the arbor aftermachining and new IBR inserted for machining. Of course, locking nut694, clamp sleeve 692 and front vertical yoke member 636 are removed topermit the shroud front portion and IBR to be slipped off the arbor.Front vertical yoke member 636 is removed by removing machine screws637.

The rear shroud portion 702 includes an opening 723 through which arborand locator sleeve pass.

The bottom of the sealing shroud 700 includes a generally rectangularflange portion 720 (FIGS. 24-25) which is adapted to be received in thegenerally rectangular recess 520 of top cover 54 with close toleranceonce the yoke assembly 630 has been pivoted about pivot pin 638 to bringthe IBR lateral center plane W into coincidence with the angle of thecenter plane H of the recess 520 at the workpart machining position M.The recess center plane angle H is selected for a particular IBR andblade design to facilitate access of the cathodes 304,306 to theopposite sides 18,20 of the airfoil blade 16' to be machined. Since theIBR center plane W has been made substantially coincident with therecess center plane H, the Z-axis slide 602 is lowered to insert therectangular shroud flange portion 720 in close tolerance fit in recess520 with the flange portion and recess thus acting as first and secondlocator means for precisely positioning the airfoil blade to be machined16' at the workpart machining position M in the electrolyte chamberbetween the cathodes 304,306 at the cathode machining position. When theflange portion is received and registered in recess 520, the hub portion10a projecting through flange opening 710 is received in recess 524 andthe blade 16' to be machine and blades immediately adjacent thereto andprojecting through flange opening 710 are received in recess 522 withample clearance. The seal member 520 in the bottom of recess 520 sealsagainst the bottom 722 of flange portion 720 of the sealing shroud 700to prevent high pressure electrolyte leakage.

Alternately as shown in FIG. 28 where like features bear like referencenumerals primed, a seal member 723' may be carried on the bottom 722' ofthe flange portion 720' of sealing shroud 700' to sealingly engage thetop of the cover 54'. A depending flange portion 725' functions as alocator means in conjunction with opening 727' in the cover 54' toprecisely position the blade to be machined.

Although the arbor 650 and IBR 10 are indexable in rotary incrementswithin the sealing shroud 700, the shroud itself is fixed in positionduring such indexing of the arbor by retaining plate 740 on horizontalyoke member 632. In particular, retaining plate 740 is closely spaced toa flat 700a on the top of the sealing shroud 700 and preventssubstantial rotation of the shroud although minor rocking thereof doesoccur.

In the ECM process or method for machining the individual oversizeairfoil blades to final dimension, the IBR is fixtured on arbor 650 withthe yoke assembly 630 retracted upwardly by movement of Z-axis slide602. In the fixtured position, the arbor 650 extends through the centralmounting hole 14 of the IBR and through the respective holes in rearportion 702 and front portion 704 of the sealing shroud and is clampedas shown best in FIG. 26. Indexer shaft 652 is indexed by motor 670 to aso-called number 1 position to place an individual airfoil blade 16' inthe central depending position with its centerline F in the machinecenter plane P substantially on the line of intersection of plane P withcathode center planes CC at the workpart machining position M ready forinsertion in the electrolyte chamber 36 between cathodes 304,306 asdescribed below. Of course, airfoil blades 16" and 16"' immediatelyadjacent blade 16' to be machined depend downwardly as shown in FIG. 42.

The yoke assembly 630 is pivoted about pivot pin 638 with screw 642 andcollar 640 loosened to place the lateral center plane W of the IBR at aselected angular relation (angle B) to the machine center plane P (FIG.3) and to the cathode center planes CC at the machining position M andcathode machining position to facilitate access to the blade 16' by thecathodes 304,306 and to place the locating flange 720 of the sealingshroud 700 at the required angle for registry with locating recess 520of the top cover 54 of the structure 34. The pivoted angular position ofthe yoke assembly 630 is releasably locked by tightening screws 642 oncollar 640.

When the Z-axis slide 602 is at the fully retraced home position forfixturing the IBR thereon, the right X-axis ram and left X-axis ram 150are fully retracted to a home position in the electrolyte chamberwherein both cathodes 304,306 are retracted along the respective left orright X-axes about two inches from machine center plane P at theworkpart machining position M to provide ample clearance. Similarly, theright Y-axis slide and left Y-axis slides 96,94 are retracted to thehome position wherein both cathodes 304,306 are retracted to the rear inthe respective left or right Y-axes to position the cathode center planeCC about one inch from its position at the cathode machining positionadjacent the workpart machining position M with center planes CCparallel with its position at the cathode machining position to provideample clearance. The electrolyte valve to the electrolyte inlet 440 isclosed and D.C. power supply (not shown) is turned off.

The machine start cycle consists of moving the cathodes 304,306 from thehome position to the coordinated position shown in FIGS. 42 and 44.Movement of right cathode 306 from the home position to the coordinatedposition involves simultaneous movement along both the right X-axis andright Y-axis by respective right hand motors 142 and 260, and movementof left cathode 304 from the home position to the coordinated positioninvolves simultaneous movement along the left X-axis and left Y-axis byrespective left hand motors 142 and 280. Although the left X-axis andY-axis movement of cathode 304 are simultaneous, they can be carried outin successive steps instead but this is not preferred. The same appliesto the movement of cathode 306 simultaneously along the right X-axis andY-axis.

It can be seen that at the coordinated position for the particular IBRshown that the cathode 304 (concave cathode) is positioned with areference centerline R1 on the cathode center plane CC and that cathode306 is positioned with a reference centerline R2 displaced or offsetfrom the cathode center plane CC. Reference centerlines R1 and R2 arereference lines that correspond to the position of the airfoil bladevertical centerline F relative to the working faces of cathodes 304,306at the finish machine position shown in FIG. 46 and are the referencelines employed to program the necessary cathode movements to obtainaccess to and machine the desired final dimension on the airfoil blade16'.

Of course, offsetting of cathode 306 in the Y-direction is effected byY-axis slide 96 and its drive motor 142. For the particular IBR shown,no offsetting of cathode 304 along the left Y-axis is required, althoughit is of course possible, to gain access to the concave side of blade16'. If the airfoil blades 16 of the IBR are inclined in the oppositedirection from that shown, then cathode 304 would be offset and cathode306 would not be; i.e. the relationship of the cathodes 304,306 tocathode center planes CC would be reversed.

From the coordinated position shown in FIG. 44, the cathodes are broughtto the cathode machining position shown in FIG. 45 aligned on oppositesides of the blade 16' at the workpart machining position M while theZ-axis slide 602 concurrently inserts the blade 16' to be machined atthe machining position M in the electrolyte chamber 36 with the shroud700 and locating recess 520 cooperating to precisely position the blade16' with its centerline F in the machine center plane P at the workpartmachining position M and substantially coincident with line ofintersection of the plane P and centerline F. The shroud and top plate54 also effect sealing therebetween as explained above when the blade16' and of course adjacent blades 16", 16"' are positioned in theelectrolyte chamber.

Movement of the cathodes 304,306 to the cathode machining position isindicated by arrows in FIGS. 42 and 44. The open circles in FIG. 44designate the ultimate positions of reference centerlines R1 and R2 atthe cathode machining position shown in FIG. 45. The cathode machiningposition of R1 and R2 relative to centerline F of the airfoil blade 16'is shown in FIG. 45.

It is clear that the cathode 306 has been moved in both right X-axis andY-axis directions to arrive at the right cathode machining positionshown. Typically, movement of cathode 306 in both these directionsoccurs simultaneously by simultaneous actuation of right drive motor 142for right ram 150 and right drive motor 260 for slide 96 carrying rightcathode support 102. It is also clear that cathode 304 has moved only inthe left X-direction with no left Y-direction movement. Movement of thecathode 304 thusly occurs concurrently with the bi-directional movementof cathode 306 as well as concurrently with downward vertical movementof Z-axis slide 602 to position blade 16' in the electrolyte chamber 36.Although rectilinear bi-directional movement of cathode 306 is shown, itwill be apparent that depending on IBR design, the bi-directionalmovement of cathode 306 may be a curvilinear path to access the blade tobe machined and obtained by suitable actuation of the drive motors forthe cathode ram and slide.

During this simultaneous movement of the blade 16' on Z-axis slide 602and cathodes 304,306 to the cathode machining position, the blades16",16"' immediately adjacent blade 16' are received in pockets 340,362of the cathodes 306,304, respectively, as illustrated in FIG. 45 withthe adjacent blades not contacting the cathodes 306,304 in whose pocketsthey are received.

During movement of the cathodes 304,306 from the coordinated position tothe cathode machining position, the sealing pistons 470 are eachactuated by their respective fluid cylinders 480 to move in coordinationwith cathodes 304,306 in the general Y-direction toward the front of thechamber 36 to engage and follow the cathode movement to the cathodemachining position. Alternatively, the sealing pistons can be actuatedto sealingly engage the cathodes after they are positioned at thecathode machining position of FIG. 45.

Once the cathodes 304,306 and blade 16' (Z-axis slide 602) arepositioned at the cathode machining position, D.C. power is supplied toanode buss 676 and hence to the IBR and blade 16' and cathode busses 121(right and left) and hence to cathodes 304,306. Copper clamp 681 isactuated by cylinder 680 to tightly grip indexer shaft 652 to insuregood electrical conductivity therebetween and also further lock theposition of the indexer shaft. And, upper and lower clamp cylinders 230associated with the left and right Y-axis slides 94,96 are actuated toclamp the slides 94,96 as described hereinabove in the Y-axis positionat the cathode machining position. The electrolyte valve is then openedto introduce flowing high pressure electrolyte; e.g. an aqueous salinesolution, through electrolyte inlet 440.

From the cathode machining position shown in FIG. 45, the cathodes304,306 are advanced along their respective left and right X-axes towardone another and toward the respective sides 18,20 of the blade 16', withadjacent blades 16", 16"' remaining in the cathode pockets out ofcontact to remove the oversize or envelope E on the blade 16' (sides18,20) as well as machine the leading and trailing edges, fillet radiiand platforms to final dimension. The cathode finish position of thecathodes is shown in FIG. 46 where it is evident that the referencecenterlines R1 and R2 are coincident with the finish machined bladecenterline F at the workpart machining position M. Advancement ofcathodes 304,306 along their X-axes is at a slower feed rate thanadvancement to the cathode machining position from the coordinatedposition.

During the machining process when the cathodes moves from the cathodemachining position of FIG. 45 to the cathode finish position of FIG. 46,high pressure electrolyte continuously discharges from inlet 440 and isguided by the sealing pistons 470 providing a flow path toward the blade16' and substantially prevented from by-passing the cathodes on the rearside thereof by the sealing engagement of the sealing pistons againstthe rear sides of the cathodes. Also, the tip of the blade 16' ispositioned against tip seal 420 to further minimize electrolyteby-passing action.

During advancement of the cathodes from the cathode machining positionto the cathode finish position, the electrical insulating layers340a,362a in each pocket 340,362 of the cathodes prevent strayelectrical currents from flowing through stagnant electrolyte in thepockets between the adjacent blades 16", 16"' in the pockets and theassociated cathodes. These adjacent blades may also be masked withelectrical insulating material to prevent such unwanted stray currents.

Once the cathode finish position of FIG. 46 is reached by the cathodes304,306, the D.C. power supply is turned off, copper clamp 681 isreleased and the rams 150 (right and left) slow feed back along the leftand right X-axes to withdraw the cathodes about .005 inch away from thefinish machined blade 16' with blades 16", 16"' still in the cathodepockets out of contact with the cathodes. The electrolyte valve isclosed and the clamp cylinders 230 are deenergized to release the Y-axisslides 94,96. The cathodes and associated rams 150 as well as Z-axisslide 602 go back to the coordinated position at a feed rateintermediate the high and slow feed rates mentioned with adjacent blades16", 16"' still out of contact.

At the coordinated position, the indexer motor 613 indexes indexer shaft652 to the next position (next slot 662) with lock plunger 664 withdrawnby cylinder 666 so as to position another airfoil blade 16 in positionfor insertion in the electrolyte chamber 36 for machining. Typically,the indexer shaft 652 will index to position every other bladesuccessively at the position for insertion in the chamber.

The cylinder 666 and plunger 664 of course are actuated to lock theindexer shaft in its new position.

The sequence of actions described hereinabove from the cathode machiningposition to the cathode finish position is then repeated to machine thenewly positioned blade and is repeated until all the individual blades16 have been machined to final dimension.

When the blade of the IBR are all machined, the cathodes 304,305 andZ-axis slide 602 are returned to the home position for removal of themachined IBR and fixturing of another IBR on the arbor for machining.

Although operation of the machine from the coordinated position to thecathode machining position has been described with cathode 306 goingthrough bi-directional movements (right X-axis and right Y-axis) andcathode 304 going through movement only along the left X-axis with noleft Y-axis movement, both cathodes 304,306 can be moved simultaneouslyindependently and bi-directionally if required by a particular IBRdesign as will be fully apparent to those skilled in the art.

While certain preferred embodiments of the invention have been describedin detail hereinabove, those familiar with this act will recognize thatvarious modifications and changes can be made therein for practicing theinvention as defined by the following claims.

I claim:
 1. In an apparatus for electrochemically machining a workparthaving appendages extending from and spaced therearound, the combinationof means for forming an electrolyte chamber, means for positioning anindividual appendage as an anode at a workpart machining position in theelectrolyte chamber with an adjacent appendage extending into theelectrolyte chamber, cathode means movable in the electrolyte chamberand having an inner working face in spaced facing relation to theindividual appendage at the workpart machining position and another faceextending transverse to the inner working face, means for relativelypositioning said cathode means and workpart in skewed relation at anangle at the workpart machining position with the inner working face inthe space between the individual appendage and adjacent appendage andwith the adjacent appendage extending toward said another face, saidcathode means having pocket means in said another face spaced behind theinner working face to receive said adjacent appendage without contact asthe cathode means is moved toward the workpart machining position andthe workpart is positioned at the workpart machining position in theelectrolyte chamber, and means for moving the cathode means in theelectrolyte chamber.
 2. The apparatus of claim 1 wherein said means formoving the cathode means moves the cathode means in multiple directionsrelative to the individual appendage as it is positioned in theelectrolyte chamber at the workpart machining position.
 3. The apparatusof claim 1 wherein the positioning means carries the workpart and ispivotable relative to the electrolyte chamber about a pivot axissubstantially coaxial with a centerline of the individual appendage atthe workpart machining position to skew the workpart at said anglerelative to the cathode means at the workpart machining position.
 4. Inan apparatus for electrochemically machining a workpart having shapedappendages, each with a first side and second side, extending from andspaced apart therearound, the combination of means for forming anelectrolyte chamber, opposed first and second cathodes in theelectrolyte chamber movable relative to a workpart machining position,means for positioning an individual appendage in the electrolyte chamberat the workpart machining position with adjacent appendages on oppositesides of the individual appendage entending into the electrolyte chamberwith said means being pivotable relative to the electrolyte chamber forskewing the workpart at an angle relative to the first and secondcathodes at the workpart machining position such that the adjacentappendages overlie a respective one of the first and second cathodes,said first and second cathodes being movable toward the respective firstand second sides of said individual appendage with each cathode havingan inner working face for positioning in spaced machining relation tothe respective first and second sides of the workpart at the workpartmachining position and another face extending transverse to the innerworking face and each cathode having a recessed pocket in said anotherface spaced behind the inner working face positioned to receive withoutcontact a respective one of said overlying adjacent appendages when theworking faces are moved to said spaced machining relation as saidindividual appendage is moved to the workpart machining position andduring machining thereof by cathode advancement toward said sides, andmeans for moving said first and second cathodes to place the respectiveworking faces in said spaced machining relation adjacent the workpartmachining position.
 5. In an apparatus for electrochemically machining aworkpart having shaped appendages, each with a first side and secondside, extending from and spaced apart around a central hub, thecombination of means for forming an electrolyte chamber, opposed firstand second electrically conductive cathodes in the electrolyte chamberdefining a cathode center plane relative to a workpart machiningposition in the electrolyte chamber, slide means movable toward theelectrolyte chamber for positioning an individual appendage in theelectrolyte chamber at a workpart machining position as an anode with acenterline of the individual appendage between the first and secondcathodes and with adjacent appendages on opposite sides of theindividual appendages extending into the electrolyte chamber with saidslide means including pivoting means pivotable along a pivot axissubstantially coaxial with the centerline of the individual appendage atthe machining position to skew the workpart centerplane relative to thecathode center plane such that the adjacent appendages overlie arespective one of the first and second cathodes, said first and secondelectrically conductive cathodes being movable toward the respectivefirst and second sides of said individual appendage, each cathode havingan inner working face for positioning in spaced machining relation to arespective one of said first and second sides at the workpart machiningposition and another face extending transverse to the inner working faceand each cathode having a recessed pocket in said another face spacedbehind the inner working face and positioned to receive without contacta respective one of said overlying adjacent appendages when the workingfaces are moved to said spaced machining relation as said individualappendage is positioned at the workpart machining position and duringmachining thereof by cathode advancement toward said sides, saidrecessed pockets each having electrical insulating means for preventingelectrical current flow between said adjacent appendages and therespective first and second cathode through electrolyte in said recessedpockets, means for supplying electrolyte to the electrolyte chamber, andmeans for moving said first and second cathodes to place the respectiveworking faces in said spaced machining relation at the workpartmachining position with said recessed pockets providing avoidance ofcontact of said first and second cathodes with said adjacent appendages.6. A machine for electrochemically machining a bladed rotor havingairfoils extending radially along a centerline from and spaced apartaround a central hub, comprising means for forming an electrolytechamber, first and second cathodes in the electrolyte chamber in spacedfacing relation and movable toward one another relative to a machiningposition therebetween, means for positioning the rotor with anindividual airfoil disposed at the machining position in the electrolytechamber with the centerline thereof between the first and secondcathodes, means for pivoting the rotor about an axis substantiallycoaxial with the centerline of the individual airfoil to skew the rotorand first and second cathodes at an angle such that first and secondairfoils adjacent said individual airfoil extend longitudinally towardthe respective first and second cathodes when the individual airfoil isat the machining position, said first and second cathodes each havingpocket means positioned to receive the respective first and secondadjacent airfoils without contact therewith at the machining position,and means for moving the cathode means in the electrolyte chamber. 7.The machine of claim 6 wherein the postioning means positions theindividual airfoil with the centerline on a vertical machine centerplane between the first and second cathodes.
 8. The machine of claim 7wherein the first and second cathodes define a cathode center planesubstantially orthogonal to the vertical machine center plane andincluding the centerline of the individual airfoil at the machiningposition.
 9. The machine of claim 8 wherein said pivoting meanscomprises a pivot member having a pivot axis substantially coaxial withthe line of intersection of the vertical machine center plane andcathode center plane.
 10. The machine of claim 9 wherein a yoke assemblyis pivotally supported by the pivot member.
 11. The machine of claim 10wherein the positioning means comprises a slide means movable toward theelectrolyte chamber on which the pivot member is disposed.
 12. Themachine of claim 6 wherein the positioning means carries the rotor abovethe electrolyte chamber and moves vertically downward to position theindividual airfoil in the electrolyte chamber at the machining position.13. The an apparatus for electrochemically machining a bladed rotorworkpart having airfoils extending radially from and spaced apart fromone another around a central hub with each airfoil having oppositelateral sides facing a lateral side of an adjacent airfoil andterminating in an end tip, the combination of means for forming anelectrolyte chamber, means for positioning an individual airfoil as ananode at a workpart machining position in the electrolyte chamber withan adjacent airfoil extending into the electrolyte chamber, cathodemeans having an inner working side facing a lateral side of theindividual airfoil at the workpart machining position and another sideextending transverse to the inner working side and movable in theelectrolyte chamber to advance the working side in the space between theindividual airfoil and adjacent airfoil in a direction transverse tosaid lateral side, means for relatively positioning said cathode meansand workpart in skewed relation at the workpart machining position suchthat the adjacent airfoil extends longitudinally toward said anotherside of the cathode means when the individual airfoil is positioned atthe workpart machining position, said cathode means having pocket meansin said another side behind the inner working side located to receivethe end tip of said adjacent airfoil without contact with said adjacentairfoil at the workpart machining position, and means for moving thecathode means in the electrolyte chamber.
 14. The apparatus of claim 13wherein the means for relatively positioning said cathode means andworkpart in skewed relation is on the means for positioning saidindividual airfoil.
 15. The apparatus of claim 14 wherein said means forpositioning said individual airfoil comprises a slide means.
 16. Theapparatus of claim 15 wherein said means for relatively positioning saidcathode means and workpart comprises a pivoting member carrying theworkpart on the slide means.
 17. The apparatus of claim 13 wherein thecathode means comprises and second cathodes on opposite lateral sides ofthe individual airfoil.